Prior Art
Seamless tubular fabrics
By assembling a warp yarn and a filling yarn in the manner of a circular or hollow wave, a radially seamless tubular fabric can be manufactured. The chief material of such warp and filling yarns is a polyester or a nylon. This seamless tubular fabric can be sliced at appropriate widths in the radial direction to provide loop-like seamless belts. The seamless belts thus obtained find application as conveyor belts, transmission belts, impact printer ink ribbon substrates and so on.
It is also a known technology to impregnate or coat such a seamless tubular fabric (or a loop-shaped seamless belt obtained by slicing it) with a resin and the present applicants also have filed several patent applications, viz.
Japanese Patent Kokai No. 61-40145 discloses a tubular article manufactured by impregnating or coating a hollow fabric woven from warp and filling yarns with a resin. However, fluorine-containing resins are not mentioned as examples of the resin.
Japanese Patent Kokai No. 64-46087 discloses a circular-woven seamless hose formed with bellows and treated with a resin and includes a cursory mention of fluororesins as the resin to be used for such resin treatment.
Raw polytetrafluoroethylene tube
A polytetrafluoroethylene powder having a primary particle diameter of about 0.2 to 0.3 .mu.m and a secondary particle diameter of about 300 to 600 .mu.m which has been separated and granulated from a dispersion prepared by the emulsion polymerization of tetrafluoroethylene is known as fine powder. This fine powder can be easily formed into fiber with a small shear force and absorbs an organic solvent, such as naphtha or white oil, efficiently to give a paste. So, as this paste is extruded to provide a preliminary molding in the shape of a round bar or a sheet which is then compressed by means of rolls to remove the solvent before spontaneous evaporation of the solvent, there is obtained a film known as green tape. The green tape thus obtained has been used commonly as a sealing material for the water pipe and other pipe joints. When sintered, the green tape gives a transparent film.
Polytetrafluoroethylene dispersion processing
A dispersion of polytetrafluoroethylene is an aqueous colloidal suspension containing a nonionic surfactant. As a cloth such as glass cloth, carbon fiber cloth or an aromatic polyamide fiber cloth is repeatedly dipped in this dispersion, dried and sintered, there is obtained an electrical insulation tape or a tape for non-bonding applications.